Created Unassigned: Feature request: allow creating an SftpClient from an SshClient instance [2712]

Currently, if I want to use the __same__ SSH session for several purposes - e.g., SFTP and SCP as well as commands I need to instantiate a new _SftpClient_ / _ScpClient_, which means a __new__ SSH connection instead of re-using the existing one. This is not a protocol requirement as SCP and SFTP are merely __channels__ same as the command or shell channel(s), which means that one should be able to create a new instance for SCP / SFTP clients from an existing _SshClient_ instance.